Published: 2014-07-28 07:57:00
Updated: 2014-07-28 18:24:14
Posted July 28, 2014
By Tony Rice
The Delta Aquarid meteor shower peaks the beginning of this week.
Meteors may be visible a few hours after sunset as the constellation Aquarius rises in the east. You will likely see more after midnight as the Earth rotates into the trail of dust left by a comet.
The best time to view is a few hours before sunrise. While the Delta Aquarids have a respectable ZHR of 20 (read on) and aren’t known for producing very bright meteors, the new moon and partly cloudy skies forecasted early this week make it worth a look.
Zenith Hourly Rate (ZHR) provides an estimate of meteors visible in an hour with the naked eye. The formula used to calculate ZHR combines the fraction of the sky blocked by clouds and trees, light pollution present, the position of the meteor shower in the sky along with the actual number of meteors observed to arrive at a number of visible meteors expected under optimal conditions.
That optimal site would have a cloud free, dark sky (such as a rural area with little to no light pollution) with an uncluttered horizon.
The radiant of the shower should be at the zenith (directly overhead) where there is a minimal amount of atmosphere between you and the meteors. This is a handicapping system of sorts allowing astronomers to compare meteor showers and observing sessions.
ZHR isn’t the only factor that impacts your meteor viewing experience.
The size of the comet trail or other particles the Earth is passing through determines whether meteors are bright or faint. Viewing is also affected by moonlight. A full moon can be orders of magnitude brighter than the meteors.
The full moon rises at sunset and sets at sunrise giving observers no break. Best viewing conditions are during a new moon, which shines the dim light reflected by Earth itself (earthshine). Last quarter moons aren’t bad either since they get out of our way quickly, setting shortly after sunset.
Next month’s Perseid meteor shower is a highlight of most years, but not this one. Perseids typically produce a lot of bright meteors, but this year a full moon during the shower’s peak will make observing difficult. Our next big meteor shower to look forward to is the Geminids in December.
The remaining meteor showers this year are:
If your observing has you up before 5:30 a.m., you might catch the International Space Station (ISS) passing over.
Tuesday, July 29, it will rise in the north at 5:25 a.m. passing just over the treetops before setting three minutes later. Thursday, July 31, it will rise from the northwest at 5:23, setting five minutes later in the east.
We will next see the ISS in the evening skies Saturday Aug. 2 at 10:02 p.m. for a very bright pass nearly directly over central North Carolina.
If clouds spoil our view in North Carolina there are some alternatives online. NASA will be streaming live from NASA's Marshall Space Flight Center beginning at 8:30 p.m. and running throughout the night. The event will feature the center’s network of all sky cameras and NASA astronomers to help spot meteors.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.